Hi, Israel.
If I recall correctly, Phill was interested in using the info to put
together a web page on the topic.
For myself and for others, I'm sorry that I haven't able to break
through to a solution on this hardware. And may well not be able to. I
invested an awful lot of time (I wasn't kidding about the last few
weeks) and learned a lot, but I can't justify spending more time on it
now, unless perhaps with an expert who merely needed me for my
hardware. So I hope that Phill will be able to standardize the content
and post this much. Then it would be great if someone with expertise
and time could push further, with or without me. The right hardware
would also be needed, but it shouldn't be too hard to locate a non-Dell
using SMM for fan control.
It's a messy, scattered, often-difficult topic, peppered with a lot of
obsolete information. From my point of view there are many unanswered
questions. Overall, it begs for better treatment.
--John
P.S. Despite the above, I may return to work on a Dell laptop soon. So
I could have a little to say about using that with the i8kutils
solution. Though that would probably be in the nature of adding some
fine points.
On 6/17/2014 10:31 PM, Israel wrote:
Hi John,
This is an intense e-mail. I think you should post this online
somewhere, and track your progress. I think there could be other
people who are looking to hack around on other hardware, that might
benefit from your in-depth study on this.
I am throughly impressed with the volume on information here.
I don't have any advice where to turn next, however. The only thing
I'd suggest testing is a few other distros to see if the fan control
works better on another one. Some distros have their kernel set up
differently, and have packages Ubuntu doesn't... so you never know.
It has helped me to track down a problem or two in the past. Puppy is
a good one to try, as they make a few version from different distros
like Ubuntu and Slackware... and it is very small to download and
doesn't require any special install to dual boot. You can copy the
files out of the ISO and boot from GRUB (which is handy if you have no
optical drive or USB booting)
Definitely let us know when you figure this out. And please add your
solution to wiki.ubuntu.com in some appropriate place. You might try
asking some specific questions in askubuntu or ubuntuforums.
On 06/17/2014 02:56 PM, John Hupp wrote:
This is a fresh attempt to summarize what I've been looking at the
past few weeks, with a nod to Phill W's request. People with more
specialized expertise will likely want to correct this in any number
of ways. Better knowledge is very much welcome.
Fan control, especially on laptops, which was my central interest, is
part of the larger topic of thermal management, which includes active
and passive methods. Fan control is the usual active method.
Passive methods include several technologies for throttling devices,
and these methods have varying effects on performance. Thermal
management has historically focused on the CPU, but has broadened to
embrace the GPU, hard drive, LCD screen, and the entire enclosure.
This has become increasingly important as form factors have shrunk.
Thermal management for a desktop is usually an easier proposition
because the heat sources are not as crammed together, because it's
easier to add fans if needed, and because the thermal management
technologies most commonly used in a desktop are, in general, better
supported, and they are more exposed by the OEM's.
The situation for laptops is, in general, the opposite of everything
just said about desktops.
*Some further orientation and outline of the various approaches*:
BIOS (presumably similar for UEFI): This is the first thing to look
at. The BIOS likely sets up some thermal management, and may present
simple or sophisticated controls in its interface. In other cases
the OEM has decided not to present any user-configurable controls
there whatsoever. When an OS has booted, the BIOS may relinquish all
or part of thermal control to it (commonly via ACPI). But it may
continue to exercise control through SMM (System Management Mode),
which temporarily suspends processing by the OS in a way that is
transparent to it, and runs some SMM BIOS code. By definition then,
it can be difficult to know what, if anything is controlled by SMM.
And SMM is platform-dependent, so there doesn't seem to be a
standards-based way for developers to write code that works across
whatever makes and models use SMM.
ACPI (Advanced Configuration and Power Interface): This is the
successor to PNP configuration and APM power management. Under ACPI,
power management is no longer the responsibility of the BIOS via APM,
but of the OS. ACPI is closely related to OSPM (Operating
System-directed configuration and Power Management), which has been
described as a system implementing ACPI. Proper functioning under
ACPI requires support by the hardware, the BIOS, and the OS. The
ACPI BIOS loads some ACPI tables into memory, the most prominent of
which is the DSDT (Differentiated System Description Table). These
tables provide hardware enumeration data and AML (ACPI Machine
Language) bytecode. The OS kernel uses an interpreter (ACPICA --
ACPI Component Architecture) to run the bytecode and employ the data
to set everything up. [A development note: ACPI was merged into the
UEFI Forum in 2013.]
ACPI and Sysfs: The state of the kernel is reflected to user space
via a sysfs, a virtual filesystem mounted at /sys. In Windows-ish
terms, this describes what device drivers are loaded and what their
settings are. But in addition to the original device nodes that
describe the kernel state most concisely, there are also symlinks to
many of the original device nodes, set up in various /sys locations,
serving various purposes. So for thermal management purposes, one
might be instructed to look at the contents of /sys/class/thermal,
but a number of the folders there are symlinks to yet other /sys
directories. Some of the kernel parameters reflected at /sys are
writable (or are supposed to be, or were at one time).
Hwmon - a sysfs extension: This extension to sysfs provides alternate
interfaces under /sys to report or control kernel parameters that may
also be represented elsewhere in /sys. But some user applications are
written such that they rely exclusively on the hwmon interfaces.
ACPI and Procfs - What is now accomplished for thermal management
purposes by the sysfs mounted at /sys, was previously accomplished by
the procfs mounted at /proc. So there is a lot of documentation
regarding, for instance, /proc/acpi/fan and
/proc/acpi/thermal_zone/*/trip_points (see
https://wiki.ubuntu.com/DebuggingACPI), but that information is now
obsolete.
Generic Thermal Management Framework - Much of thermal policy or
decision-making has been handled in the OS by the kernel, but exposed
to some degree to user control via sysfs. The idea under this
framework is reduce the role the kernel plays to that of a
facilitator, and leave policy/decision-making to user-land tools.
But worth noting is that such user tools do not fundamentally add to
lower-level methods.
*SOLUTIONS* (check the standard repositories first for any additional
packages you want to download)
BIOS: Start here. This may be all you need to improve your fan
control. Sometimes an updated BIOS is required.
lm-sensors + fancontrol (http://www.lm-sensors.org): This solution
explicitly relies on the hwmon interfaces of /sys, and it only works
with PWM (pulse-width modulated) fan controllers, not with
voltage-regulated controllers (and no, I don't know why on either
count). But its README says this:
Laptops, on the other hand, rarely expose any hardware monitoring
chip. They often have some BIOS and/or ACPI magic to get the CPU
temperature value, but that's about it. For such laptops, the
lm-sensors package is of no use (sensors-detect will not find
anything), and you have to use acpi instead.
ACPI - Editing/creating thermal trip points: Regarding thermal
management, you will see documentation that commands like these
should change the thermal trip point temperature:
$ sudo sh -c "echo 75000 >
/sys/class/thermal/thermal_zone0/trip_point_1_temp"
or
$ echo 75000 | sudo tee trip_point_1_temp
But this does not seem to be supported by recent kernels and yielded
"Permission denied" errors in my tests. I have seen conflicting
information on whether trip points should be editable.
Concerning laptops, there is this statement at
https://01.org/linux-acpi/documentation/debug-how-isolate-linux-acpi-issues:
"Most notebooks also use native fan control instead of ACPI. There
are, however, a couple of notable exceptions: HP/Compaq, Acer, and
Fujitsu-Siemens often use ACPI-based fan-control."
ACPI - Overriding the DSDT table: There is documentation (e.g.
Patching DSDT in recent Linux kernels without recompiling
<http://blog.michael.kuron-germany.de/2011/03/patching-dsdt-in-recent-linux-kernels-without-recompiling/>)
about how to edit the DSDT table that the BIOS presents to the
kernel, and then direct the kernel to use the edited table. One
wonders about that as a method for creating/modifying ACPI thermal
trip points. I have not tried it. One source with more expertise
says that this *might* work, but notes that if a fan is controlled by
SMM, this may overrule something set up in ACPI.
i8kutils (i8kctl
<http://manpages.ubuntu.com/manpages/trusty/man1/i8kctl.1.html> and
i8kmon
<http://manpages.ubuntu.com/manpages/trusty/man1/i8kmon.1.html>):
This relies on SMM, and as a platform-dependent solution, the authors
are aiming to support only Dell laptops. But this is probably the
best solution for those.
thinkpad-acpi
(http://www.thinkwiki.org/wiki/How_to_control_fan_speed): This is an
extension of the ACPI support provided by the standard kernel. Note
that it does not support all Lenovo laptops. Lenovo 3000's, for
instance, are not Thinkpads and are not supported by this extension.
Asus: See
http://forum.notebookreview.com/asus/705656-fan-control-asus-prime-ux31-ux31a-ux32a-ux32vd.html
and https://gist.github.com/felipec/6169047 and
https://help.ubuntu.com/community/AsusZenbookPrime#Sensors_.28temps_.26_fans.29
as good starting points.
Thermald: See the links following for information about the thermal
daemon new to 14.04. It is an implementation of the Generic Thermal
Management Framework. It controls cooling via
- the Running Average Power Limit (RAPL) driver (Sandybridge upwards)
- the Intel P-state CPU frequency driver (Sandybridge upwards)
- the CPU freq driver
- the Intel PowerClamp driver
- active or passive cooling devices as presented in sysfs (but it
cannot create any new devices; if there is no FAN device, it will not
control the fan)
https://wiki.ubuntu.com/Kernel/PowerManagement/ThermalIssues
http://manpages.ubuntu.com/manpages/trusty/en/man5/thermal-conf.xml.5.html
https://01.org/linux-thermal-daemon/documentation/introduction-thermal-daemon
http://www.linux.com/news/featured-blogs/200-libby-clark/721494-linux-thermal-daemon-monitors-and-controls-temperature-in-tablets-laptops
*MY CURRENT CASE*
I wanted the fan to start at a lower temperature on a Lenovo 3000
C200 laptop.
The BIOS exposes no thermal settings. But someone who previously
made a serious attempt at this on a Lenovo 3000 N200 says that the
fan is controlled by SMM. This makes sense, since the fan trips at
the same temperature in Windows or Lubuntu. It's notable that active
cooling is done via SMM, while passive cooling is via ACPI.
Lm-sensors: It does not find a PWM controller that it can work with.
ACPI: There are only two trip points defined, both passive, and the
lowest of them at 87C. There is no FAN device in /sys/class/thermal,
and attempts to modify trip point settings resulted in "Permission
denied." I still wonder if editing the DSDT table might net me any
gains, but I decided for the time being not to invest any more time,
especially with the prospect that SMM would undo my work.
Thinkpad-acpi: It does not support the Lenovo 3000.
Thermald: I installed this with high hopes, but found out that it
cannot control a fan if an ACPI fan device does not already exist.
And since this laptop does not have a SandyBridge or newer processor
to take advantage of the RAPL or P-state drivers, thermald does not
bring much to the table that ACPI did not already provide.
Further recourse: The only measures I can imagine now are to write
something like i8kutils for this Lenovo platform. Or edit the DSDT
table just to see what happens. I say "imagine" because I will very
likely do neither! One source also mentioned the prospect of
controlling the embedded controller for the fan via hwmon, but I
haven't seen any details on how to accomplish that apart from lm-sensors.
A small bit of consolation: I recall that Speedfan regards 50C as a
good trip point, and thermald will try to keep the CPU under 45C.
But I have read that it's generally OK for laptops to run somewhat
hotter than desktops. This laptop fan kicks on around 68C and seems
to hold the line pretty well, so maybe the thermal management is not
as bad as I first thought.
--
Regards
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